An experimental investigation has been carried out for fully developed turbulent flow in a rectangular duct with large aspect ratio (11:1) and having expanded metal mesh as artificial roughness. The effect of expanded metal mesh geometry [i.e. relative longway length of mesh (L/e), relative shortway length of mesh (S/e) and relative height of mesh (e/D)] on the heat transfer coefficient and friction factor has been investigated. The range of the system and operating parameters included L/e from 25 to 71.87, Sie from 15.62 to 46.87 and e/D from 0.012 to 0.039 for Reynolds numbers from 1900 to 13 000. Correlations for the Nusselt number and friction factor in terms of these parameters have been developed that can correlate the experimental data reasonably well.